Optimizing precipitation hardening in a L1₂-strengthened medium-entropy alloy via tuning the anti-phase boundary energy

In present work, we investigate the elemental partition behaviors in L1₂ ordered intermetallics and its influence on mechanical properties in a Ni-Co-Cr-Al-Ta medium-entropy alloy (MEA) system through a combination of density functional theory (DFT) calculations and experimental investigation. Our finding reveal that Ta has a strong tendency to occupy Al sublattice, while Co prefers Ni sublattice, Cr, on the other hand, randomly occupy Al and Ni sublattices, resulting in the formation of the multicomponent (Ni, Co, Cr)₃(Al, Ta, Cr) L1₂ intermetallics. Among the constituent elements, Ta is identified as an efficient element for enhancing hardening of the alloy. Furthermore, we demonstrate that improving Ta/Al ratio leads to a significant increase in anti-phase boundary (APB) energy, resulting in superior precipitation hardening effects and excellent mechanical properties. Our founding provide valuable insights for further the rationally design and rapid development of high performance L1₂-strengthened alloys.